Liquid dielectrics and apparatus embodying the same



' Liquid Dielectric June 24, 1958 c. w. LEWIS 2,340,627

LIQUID DIELECTRICS AND APPARATUS EMBODYING THE SAME Filed Sept. 4, 1952 Fig. l.

20 Q Comprising 'o Halogenaied Aromatic Compound ,an Epoxide Scavenger and a Basic Niirogenous Compound L0 Fig. 2.

No Tribenzyiamlne Tribenzylamine 0.000262M 0.000i3lM IO 20 30 40 WITNESSES: Time- Minutes INVENTOR Reaciion Ra'ies of Absorption of HCLby Phenoxy Propane Oxide Charles W. Lewis ATTORNE states Qffice 254M Patented June 24, 1958 The major portion, about 95% to 99.9%, of the di-' electric composition comprises halogenated aromatic com- 2,840,627 pounds such, for example, as chlorinated diphenyl, chlo- 1 rinated benzene, chlorinated alkyl benzene, and mixtures LIQUID gg gggi g i gfig 5 thereof. A widely employed composition comprises at least 50% by weight of chlorinated diphenyl in which Charles W. Lewis, Pittsburgh, Pa., assignor to Westingfrom 40% to 60% of the hydrogen atoms have been rehouse Electric Corporation, East Pittsburgh, Pa., a corplaced with chlorine, for instance, pentachlorodiphenyl, Pofatloll 0f sylvania the remainder of the composition being a chlorinated Application September 4, 1952, Serial No. 307,933 E232: compound such, ror example, as trichloro- 5 Claims. (Cl. 174-17) The halogenated aromatic dielectric has admixed therewith from 0.05% to 5% by weightof an epoxy compound having the group This invention relates to novel liquid dielectric com- -oH-onpositions and electrical apparatus embodying the same.

At the present time, halogenated aromatic compounds 1 are employed extensively as liquid dielectrics for insulat- The P Y mpound functions as a s av ng any ing electrical apparatus. In particular, chlorinated dievolved hydrogen Chlohde, slhce 1t W Wlth h' phenyl base compositions are employed in transformers hydrogen chlhrlde t0 Prodhc6 a y lneftl'efictlon for cooling and insulating the windings thereof. How- Product Shltahle 19 2 3 Fomphhhds are glyfhdol and ever, an electrical arc in the apparatus will cause diselhers thereof, and derlvahves of ethylene f P sociation of the chlorinated diphenyl with evolution of h examples thereof arh, phhllhxyp ropehe Oxide 3" hydrogen chloride. The hydrogen chloride w attack cidyl allyl ether, benzyl ethylene oxide, styrene oxide, the copper, paper and other materials employed in the 1,3 P YP P9 Y) and construction of transformers. Many electrical arcs perepoxypropoxy)dlphelly]hlmethyhhethahe- MlXtllYeS 0f sist for only a brief period of time and if there were some y two more Of lCh epoXy compounds may be means available for absorbing the evolved hydrogen employedchloride, no corrosion or deterioration of a permanent It has been fhscov ered that the Tale of reachoh of d i bl nature, would k placg hydrogen chloride with the epoxy compounds is such It has been suggested to include in the halogenated that a Prohmged P P of hmh Teqhhed t0 h dielectrics a scavenger capable of removing or reacting say, 99% of the hyhl'ogeh h Teachoh h with the hydrogen chloride. To be effective in removing 9 M the hydrogen Chlohde from a glveh small amounts of evolved hydrogen chloride, any scavdlelectflc h vlng 0.001 mole of H Cl present may be as anger h ld b pidl efiectivg to prevent the hydrogen much as to 60 minutes. It Will be appreciated that chloride from materially reacting with copper, iron and f to lfmgfeachon hydrogen ChlOrlde the other materials employed in the transformer. 1h thehlelhctflc Wlh react appreclably pp l The object of this invention is to provide a novel liquid lose: lmh and other I Whlch the elecmlcal di l i composition csmprising halogenated aromatic apparatus is constructed. it is desirable mat the reaction compounds, an epoxy Compound and a basic nitrogenous 40 t me be substantially reduced so that the hydrogen chlocompound capable of, forming asalt with hydrogen halide, ride W111 he feHlOVed by reaction with the epoxy comwhereby the rate of reaction of the epoxy compound with P at a h greater rate olhfil' that y traces of wowed h d hands is greatly accgleratei hydrogen chloride be present 111, for example, from 10 to Another object of the present invention is to provide f h H has been avowed from the hale electrical apparatus embodying a halogenated aromatic gehated chelectrlcdi l i 1i id at least one epOXy compgund, and a In order to greatly accelerate the rate of reaction of tertiary amine capable of forming a salt with hydrogen the epoxy compound Wlth d g Chlonde, I have halide, whereby the rate of reaction f the epoxy found that smallamounts of basrc nitrogenous compounds pound ith l d h d h lid i the liquid capable of forming a salt with hydrogen chloride, as well electric is greatly accelerated, 59 as the hydrogen chloride salts thereof, should be added Other objects of the invention will, in part, be obvious to the halogenated dielectric containing an 2 3 and will, in part, appear hereinafter. For a better under- P If the basic nitrogenous chmpouhds are Present standing of the nature and objects of the invention referin thh liquid dielectric, y hydrogen ChlOfide generated ence should be had to the following description and therein Subsequently will p p y form the hydrochlo' drawing, in which: ride salt thereof. The basic nitrogenous compounds and Figure l is a view in elevation, partly in ti f a their hydrochloride salts comprise amines, guanidines transformer, and and quaternary ammonium compounds. Tertiary amines Fig. 2 is a graph plotting against time th am t f are particularly suitable. Specific examples are tribenzylhydrogen chloride remaining in a given composition preamine, primary benzylamine, octylamine, dibutylamine, pared in accorda ce with the invention. 60 diphenyl guanidine, and the hydrogen chloride and hy- 1 have discovered that chlorinated aromatic dielectric drogen bromide salts of each of the foregoing, and cetyl liquids may be combined with (a) certain epoxy comtrimethyl ammonium bromide. pounds which will react with evolved hydrogen halide The amount of these basic nitrogenous compounds or and (b) extremely small amounts of basic nitrogenous halide salts may be as little as 0.001% of the Weight of compounds which form salts with hydrogen halide, such the liquid dielectric and will provide a substantial increase salts either being formed in situ or originally added, in reaction rate of the hydrogen chloride with the epoxy which salts greatly accelerate the rate of reaction of the compound. Considerably more of the basic nitrogenous hydrogen halide with the epoxy compound, whereby any compounds may be added, for example 0.02% by Weight evolved hydrogen halide is rapidly absorbed or reduced or more. It is preferable to add the non-halogenated basic to harmless proportions and thereby any electrical appanitrogenous compound because it is readily soluble in the ratus embodying such dielectric composition is rendered dielectric. It is desirable not to add the basic nitrogenous more effective. compound in amounts larger than the saturation limit V creases rapidly.

of the resulting hydrochloride salt thereof. The basic nitrogenous compound is considerably more soluble in the halogenated aromatic dielectrics than the hydrochloride salt thereof. Any excess of the'basic nitrogenous compound will result ina fine precipitate forming when hydrogen chloride is subsequently evolved in the dielectrio and such precipitate is quite difiicult to remove from the surfaces of the electrical membe Referring to Fig. 1 of the drawing, there is illustrated a transformer comprising a sealed casing 12 including a cover 14 through which are disposed bushings having conductors 18 in circuit with a coil 20 within the casing. The coil 20 comprising one or more electrical conductors is immersed in a liquid dielectric 22 to provide for insulating the electrical conductors and for dissipating the heat evolved during operation thereof to the walls of the casing 12. The dielectric 22 comprises a halogenated aromatic compound or a mixture of two or more such compounds, an epoxy scavenger and a reaction accelerator comprising a basic nitrogenous compound, for example, tribenzylamine. Ordinarily, it will be preferable to mix the components of the dielectric 22 before it is introduced into the casing l2. However, the separate components may be individually placed within the casing 12 and they will readily admix by mutual solution.

If an-electrical arc occurs in the conductors. 18 or winding 20, the halogenated aromatic compound will be dissociated to produce hydrogen halide. When this occurs,- the epoxy compound will react with the hydrogen halide at a given rate. However, the rate of reaction de- The tribenzylamine will be promptly converted to the hydrogen halide salt and the resulting hydrogen chloride salt will increase the rate of reaction between the hydrogen halide and the epoxy compound to a marked degree.

hydrogen chloride concentration.

Referring to Fig. 2 of the drawing there is illustrated the reaction curves of four different compositions. Each composition comprised approximately 99.9% by weight of a mixture comprising 60% diphenyl and by weight of trichlorobenzene, and 0.11% by weight of phenoxypropene oxide. Four separate lots of this composition were prepared. To one of the lots there was added 0.00l2% by weight of tribenzylarninehydrochloride; to another lot there was added 0.0024% by weight of'tribenzylaminehydrochloride; and to the third one there was added 0.0049% by weight of tribenzylaminehydrochloride; and the fourth lot had no amine present therein. Into each of the four lots of the liquid compositions so prepared, there was added approximately 0.0005 mole per liter of hydrogen chloride. The amount of free hydrogen chloride remaining in each lot was determined at short intervals of time, and the fraction of free hydrogen chloride remaining wasplotted against time as shown in Fig. 2 of the drawing.

Curve A was drawn from the lot containing no tribenzylaminehydrochloride additive. It will be seen that even after 40 minutes, approximately 15% of the added hydrogen chloride Was still free. The reaction rate was decreasing with decrease in concentration of hydrogen chloride. I would have required several hours to reduce the amount of free hydrogen chloride to a few percent of the originally added hydrogen chloride. Curve B shows the rate of reaction when 0.0012% of tribenzylaminehydrochloride is present. The rate of reaction has been so greatly accelerated over the rate taking place in the lot for which curve A Was drawn, that at the end of approximately 25 minutes, there is less than 8% of the original hydrogen chloride present in the liquid. Curves C and D indicate progressively more rapid rates of removal of the hydrogen chloride. it will be appreciated that only extremely small fractions of the free hydrogen chloride are present after amatter of less than 20 minutes in the lots of compositions of curves C and D. Therefore, the corrosive action and deterioration caused by the by weight of pentachloro- 7 whereas with the salt of the basic nitrogenous compound present the rate is proportional to the first power of the Other tests show that the addition of the tribenzylamine, as such, the small amounts indicated herein to the liquid dielectric will accelerate the removal of the hydrogen chloride by the epoxy compound in a similar fashion. When 0.02% of tribenzylamine is present the reaction is, so rapid that there is no practical way of measuring the concentration of residual hydrogen chlo-,

ride. In only a few minutes there has been substantially complete removal of the hydrogen chloride by the epoxy compound.

In the small amounts herein indicated the basic nitrogenous compounds are not harmful to the liquid dielectric The tertiary amines are not ionized substantially in the dielectrics and have little or no efiect on the dissipation factor of the dielectric.

The invention has been described with reference to specific compounds, but it is to be understood that such illustrations are exemplary and not limiting.

I claim as my invention:

l. A dielectric composition consisting essentially of a chlorinated aromatic dielectric liquid asthe major component, the halogenated aromatic liquid giving off hydrogen chloride when subjected to arcing, from 0.05% to 5% by weight of at least one epoxy-compound having the group dissolved in the dielectric liquid, hydrogen chloride, and from 0.001% by weight ofa tertiary amine capable of forming a salt with hydrogen chloride up to the amount that produces a saturated salt solution whereby the rate of reaction of the epoxy com:

pound with evolved hydrogen chloride is accelerated.

2 A dielectric composition comprising at least about by Weight of chlorinated aromatic compoundssclected from the group consisting of 40% to 60% chlorinated diphenyl, and chlorinated benzene, at least half the weight of the chlorinated aromatic compound being chlorinated diphenyl, from 0.05% to 5% by weight of phenoxypropene' oxide and from 0.001% to 0.02% by weight of tribenzylamine to accelerate the rates of reaction between the phenoxypropene oxide and any hydrogen chloride evolved from the chlorinated aromatic compound.

3. A dielectric composition consisting essentially of a chlorinated aromatic dielectric liquid as the major component, the halogenated aromatic liquid givin off hydro gen chloride when subjected to arcing, from 0.05% to 5% by weight of at least one epoxy compound having the group CHOH- dissolved in the dielectric liquid, to react with any evolved hydrogen chloride, and at least 0.001% by weight of an accelerator selected from the group consisting of basic nitrogenous compounds and hydrochloride salts thereof, up to the amount that produces a saturated hydrochloride solution the halogenated liquid dielectric.

4. Electrical apparatus comprising, in combination, a casing, an electrical conductor in to react with any evolved the casing, and a liquid dielectric disposed in the casing to insulate the conductor and to dissipate heat developed in the conductor, the dielectric consisting essentially of a chlorinated cyclic dielectric liquid as the major component, the halogenated cyclic liquid giving oii hydrogen chloride when subjected to arcing, from 0.05% to 5% by weight of at least one epoxy compound having the group electric comprising essentially 95% by weight of chlorinated cyclic compounds selected from the group consisting of to chlorinated diphenyl, and chlorinated benzene, at least halt the chlorinated cyclic compound being chlorinated dipl'tenyl, from 0.05% to 5% by weight of phenoxypropcne oxide and from 0.001% to 0.02% by weight of tribenzylamine.

References Cited in the tile of this patent UNITED STATES PATENTS 2,094,367 Missbach Sept. 28, 1937 2,672,504 Hardy Feb. 3, 1953 FOREIGN PATENTS 601,359 Great Britain May 4, 1948 OTHER REFERENCES Berberich et al.: J. Ind. & Eng. Chem., Jan, 1948, vol. 40, N0. 1, page 118. (Copy in 317-259.) 

4. ELECTRICAL APPARATUS COMPRISING, IN COMBINATION A CASING, AN ELECTRICAL CONDUCTOR IN THE CASING, AND A LIQUID DIELECTRIC DISPOSED IN THE CASING TO INSULATE THE CONDUCTOR AND TO DISSIPATE HEAT DEVELOPED IN THE CONDUCTOR, THE DIELECTRIC CONSISTING ESSENTIALLY OF A CHLORINATED CYCLIC DIELECTRIC LIQUID AS THE MAJOR COMPONENT, THE HALOGENATED CYCLIC LIQUID GIVING OFF HYDROGEN CHLORIDE WHEN SUBJECTED 